Sensing and control apparatus for classifiers



Dec. 17, 1963 J. P. M CARTY ETAL SENSING AND CONTROL APPARATUS FORCLASSIFIERS Filed March 1, 1961 2 Sheets-Sheet 1 GRINDING MILL CI/zcu/ra I l ,8 22 EXHAUST R! [9a 19 u 42 a L 1' 40\ i i 37 I i 31 L "fi'.

0- SUPPLY JAMES R MCART) Cl/A/FLES H. CggPf/S A TTORNE Y5 Dec. 17, 1963J. P. MCCARTY ETAL 3,

SENSING AND CONTROL APPARATUS FOR CLASSIFIERS Filed March 1, 1961 2Sheets-Sheet 2 ORE PROPER SIZE FIN/SHED MATERIAL INTAKE STORAGE CONTRGLVAR/ABLE I .spsso CONTROL 47 GRIND/N6 MILL PUMP JAMES I? M CAIRT)CHARLES H. CURTIS INVENTORSI United States Patent 3,114,510 SENSING ANDCONTROL APPARATUS FOR CLASSIFIERS James P. McCarty and Charles H.Curtis, Tucson, Ariz.,

assignors to Duval Sulphur & Potash Company, Houston, Tex., acorporation of Texas Filed Mar. 1, 1961, Ser. No. 92,695 18 Claims. (Cl.241-3 4) This invention relates to new and useful improvements in asensing and control apparatus for cyclone classifiers. Moreparticularly, it relates to the control of the underflow discharge of acyclone classifier by sensing the configuration of the pattern of saiddischarge.

As is well known, classifiers of the cyclone type comprise a cylindricalupper body section and a lower conical section and utilize centrifugalforce to effect the classification or separation of material. Experiencehas shown that the configuration or pattern of the underflow dischargeof the cyclone varies from axial under overload conditions to a flaringwide-angle discharge under underload conditions, so that saidconfiguration or pattern is directly related to operation conditionsand, therefore, is indicative of the separation efficiency of theclassifier. Overloading of the cyclone results in undesirable coarsematerial being carried over into the overflow section and dischargedwith the proper size finished material; on the other hand, duringunderload conditions finished material is undesirably carried out in theunderflow. The existence of either of these conditions, that is,underload or overload, interferes with optimum separation and maximumefficiency of operation. Since the configuration or pattern of theunderflow discharge is responsive to overload or underload conditions,said pattern provides an accurate and convenient indication or measureof the separation eflEiciency of said classifier.

It is therefore the primary object of this invention to provide asensing apparatus for accurately sensing the configuration of theunderflow discharge pattern of a cyclone 'whereby said sensing meansprovides information as to said configuration and, therefore,information as to the efficiency of operation of said unit asrepresented by the configuration of the underflow discharge.

An important object of this invention is to provide a control apparatushaving means for maintaining the configuration or pattern of theunderflow discharge of a classifier within certain predetermined limitsto thereby maintain the operation of the classifier within an eflicientseparation range.

A further object is to provide control apparatus for cyclone classifierswhich will automatically control the configuration of the underflowdischarge by automatically varying the size of the underflow dischargeorifice or apex valve of said classifier in response to a change in saidunderflow discharge configuration.

A still [further object is to automatically control the configuration ofthe underflow discharge by automatically varying the input load to thecyclone in response to a change in the underflow discharge pattern.

Another object is to provide an improved apparatus of the characterdescribed which lends itself to use with a single control means or witha combination control means for effectively varying and controlling theconfiguration or pattern of the underflow discharge and which may, ifdesired, be utilized to actuate an alarm or signal, such as a bell orlight.

Another object is to provide an improved apparatus of the characterdescribed which lends itself to use with a single control means or witha combination control means for effectively varying and controlling theconfiguration or pattern of the underflow discharge of cycloneclassifiers and which may, if desired, be utilized to regu- 3,114,510Patented Dec. 17, 1963 2 late the rate of feed input to a grindingcircuit in order to maintain the desired volume of circulatingclassifier sand load for eflicient closed circuit grinding operation.

The construction designed to carry out the invention will be hereinafterdescribed, together with other features thereof.

This invention will be readily understood from a reading of thefollowing detailed description and reference to the drawings wherein:

FIGURE 1 is a diagrammatic illustration of one embodiment of the presentinvention wherein the signal generated by the sensing means is utilizedto vary the size of the underflow discharge orifice, and

FIGURE 2 is a diagrammatic illustration of a second form of the presentinvention wherein the signal generated by the sensing means is utilizedto automatically vary the input load to the cyclone.

Referring now to FIGURE 1, the conventional cyclone classifier 10comprises an upper cylindrical section or feed chamber 11 and a conicalor tapered section 12 which extends downwardly from said upper sectionor chamber 11. The upper section 11 has a tangentially disposed inlet 13in its wall, and said inlet has connection with a feed supply or inletconductor 14, whereby the feed material may be introduced into the upperend of the classifier. The overflow material which is separated in saidclassifier escapes from the upper portion thereof through an axiallydisposed tube or vortex finder 15 which communicates through an elbow 16with an overflow discharge conduit 17.

The conical section 12 is normally disposed to direct its reduced end orapex downwardly, and the heavier phase material which is separated inthe classifier escapes through the open lower end of said section. Suchlower end is formed with an external annular flange 12a, and a dischargecontrol or apex valve 18 is mounted adjacent to said flange, said apexvalve being secured in position between the flange 12a and a similarflange 19a provided on the upper end of the tubular discharge nozzle ortailpipe 19. Suitable bolts 20 extend between the flanges 12a and 19a tomount the apex valve 18 in position.

The discharge control or apex valve 18 has a variable bore or opening 21extending therethrough, and such opening functions as a variabledischarge orifice for the underflow, i.e., the material discharging fromthe lower end of the classifier. As is well known, the cycloneclassifier is usually disposed with its apex directed down- Wardly, butsaid classifier may be operated with its axis in other than a verticalplane. However, for the purposes of the present description the materialdischarging from the apex will be referred to as the underflow and it isto 'be understood that such term shall include such discharging materialirrespective of the particular disposition of the classifier.

The valve 18 may take any of several physical forms but, as illustrated,one form of said valve includes an annular resilient or flexibletube-like element 22, the interior of which is connected with a pressurefluid line 23. Variation of pressure within the interior of the element22 will expand or contract said element to vary the size of the bore oropening 21 through said element and thereby vary the size of theunderflow discharge orifice of the classifier. As is well known,variation of the size of said discharge orifice will change the configuration or pattern 24 of the material discharging from saidclassifier.

In the operation of the cyclone classifier 10, the feed stock enters theupper cylindrical section 11 through the inlet conductor 1'4 and thetangential feed inlet 13 and is subjected in the usual manner to awhirling centrifugal action within the sections 11 and 12. The heavierphases of the material are thrown outwardly toward the walls of theconical section 12 where said heavier materials collect and passdownwardly through the underflow discharge orifice 21 of the apex valve18 and then outwardly through the tailpipe 19. The finer, less coarsematerials move toward the center of the cyclone and are drawn into thevortex finder 15 and pass therethrough into the elbow 1 6 and theoverflow discharge conduit 17.

As noted above, the configuration or pattern 24 of the underflow isdirectly related to the operating efficiency of the cyclone and is thusindicative of the effectiveness of the separation occurring within thecyclone. The angle A described by the lines 24a and 241) represents ordefines the preferred range or area within which the outer surface ofthe underflow is to be maintained for maximum efficiency and optimumseparation. As will more fully appear hereinafter, when the outersurface of the underflow is not within this range the cyclone is notoperating at maximum efficiency, and the desired separation orclassification of the feed is not being obtained; and it becomesdesirable to make certain operating changes or corrections which willinsure operation of the cyclone at maximum efficiency.

When the cyclone is operated under underload conditions, the outersurface of the underflow extends beyond or outwardly of the preferredouter limit line 24b. Under these conditions, too much of the feedpasses through the underflow discharge opening 21, and the desireddegree of separation does not occur. Thus, particles of the desired sizeto be separated pass out of the cyclone in the underflow rather thanthrough the overflow discharge elbow 16.

Under overload conditions, the outer surface of the underflow is withinor centrally of the preferred inner limit line 24a. Under theseconditions, the underflow is generally said to be ropy, as indicated bythe dotted lines 25 and 26 in FIGURE 1. When the underflow pattern hasthis ropy configuration, undesirable coarse materials are carried overthrough the overflow discharge elbow 16, and the cyclone may becomeinoperative due to plugging.

As is well known, underload conditions may occur for several reasons.For example, when the quantity of feed stock introduced into the cycloneclassifier through feed inlet nozzle 13 is less than that quantity atwhich optimum separation of particles and maximum efficiency areobtained, or when the underflow discharge opening 21 is too large for agiven desirable rate of feed, or when the constituency of the feed, suchas the coarseness of the grind, varies appreciably during operation,even though there is no change in feed rate. As noted previously, aflaring wide-angle underflow discharge pattern is indicative of suchunderload conditions. Conversely, overload conditions may occur when thequantity of feed stock introduced through the feed inlet nozzle 13 isgreater than that quantity at which optimum separation of particles andmaximum efficiency are obtained or when the underflow discharge orifice21 is too small or restricted for a given desirable rate of feed or whenconstituency of the feed changes. Such overload conditions are indicatedby a more axial or ropy underflow pattern.

For sensing and ultimately controlling the underflow pattern 24 in orderto maintain the outer surface of said underflow pattern within thedesired limits 24a and 24b to preclude the foregoing disadvantages, asensing means is provided.

The sensing means includes an outer sensing element or probe 29 which issuitably supported by an adjustable bracket or other support 291) so asto locate its extremity 29a at the outermost li-mit line 24b of thepattern 24, which is the point at which satisfactory operation isobtained. The sensing means also includes an inner sensing element orprobe 30 which is suitably supported by an adjustable support 36b so asto locate its extremity 30a at the innermost limit line 24a of pattern24 at which satisfactory operation is obtained. The probes areconstructed to provide a signal when the material of the underflow iscontacting said probes and to provide a different signal when saidmaterial is out of contact therewith. Therefore, if the underflowpattern is such that its outermost surface, as indicated by line 24b,moves outwardly of the outer probe 29, the end 29a of said probe iscontacted by underflow material and a signal is generated. On the otherhand, if the underflow pattern is such that its outermost surface, asrepresented by line 24a, moves inwardly of the end 3611 of probe 30, nomaterial is contacting probe 30 and a signal is generated. The signalsgenerated by probes 29 and 30 may be readily utilized to indicate thatthe outer surface of the underflow is not within desired limits.

Although any type of sensing element which will generate a signal uponcontact or noncontact with the material may be employed, one type whichhas been found satisfactory is one which is capable of connection in anelectrical circuit, with the circuit being opened and closed by contactor noncontact of material with the element, and the elements 29 and 3!}are of this type. The element 29 has electrical connection throughconductor 31 with an electrically-actuated controller 32; a conductor 33eXtends from the controller and is connected to the metallic tailpipe19, and with this arrangement the electrical circuit between tailpipeand element 29 is completed by the underflow material. In a similarmanner the element 30 has electrical connection through conductor 34with an electrically-actuated controller 35; a conductor 36' extendsfrom the controller 35 and is connected to the metallic tailpipe 19, theelectrical circuit between tailpipe 19 and probe 30 being completed bythe underflow material. Thus, it will be seen that an electrical circuitis affected in accordance with the contact or noncontact of underflowmaterial with the sensing probes.

The controller 32 may have electrical connection with an alarm 37 toactuate said alarm when the outer surface of the underflow comes incontact with the probe 29. Also, the controller 35 may be connected withsaid alarm to operate the same when the outer surface of the underflowmoves out of contact with the inner probe 30. When the alarm 37, whichmay conveniently be a bell or light, is actuated, manual corrections oradjustments of the operating conditions of the cyclone may beaccomplished so that the outer surface of the underflow will be broughtwithin the preferred range A, whereupon the alarm 37 will no longer beactuated.

It is preferable that automatic control of the underflow pattern 24 beeffected, and in FIGURE 1 is shown an apparatus for varying the size ofthe underflow discharge orifice 21 so that the outer surface of theunderflow may be maintained within the preferred range A.

The outer probe 29 operates in the manner previously discussed,completing the electrical circuit through the controller 32 when theouter surface of the underflow moves out of the preferred range A andcomes into contact with the said probe 29. The controller 32, by meansof well known electrical circuits, then causes the relay 38 to open thepressure fluid supply valve 39, whereupon the pressure fluid, such asair, may enter the flexible annulus 22 through the conduits 40 and 23.The resulting expansion of the annulus 22 restricts or reduces the sizeof the underflow discharge orifice 21, and as the size of the orifice 21is reduced the outer surface of the underflow moves inwardly or axiallyinto the preferred range A, whereupon contact between the outer probe 29and the underflow is broken. This opens the circuit connecting the probe29, controller 32 and tailpipe 19, and the controller 32 then operatesto close the supply valve 39.

When the outer surface of the underflow moves inside or centrally of theinner limit line 24a and out of the preferred range A, contact betweenthe underflow and the inner probe 30 is broken, thereby opening theelectrical circuit of which the controller 35 is a part. In response totheopening of said circuit, the controller 35 operates to open thepressure fluid exhaust valve 41 by any well known means, such aselectrical connection with the relay 42. When the exhaust valve 41 isthus opened, the air within the resilient annular valve member 22escapes therefrom through the conduits 23 and 43. The resultingcontraction of the valve member 22 increases the size of the underflowdischarge orifice 21, and the outer surface of the underflow movesoutwardly into the preferred range A. When the underflow contacts theinner probe 30, the circuit through controller 35 is completed and theexhaust valve 4-1 is closed, thereby trapping the pressure in the valvemember 22.

Thus, the size of the underflow discharge orifice 21 is automaticallymaintained at that size for which the outer surface of the underflow iswithin the preferred range A. It will be understood that anysatisfactory fluid, in addition to air, may be used as the pressurechanging means so as to vary the pressure within the flexible annularvalve member 22. Furthermore, there are several types of variableunderflow discharge orifice valves, such as the disc type, commerciallyavailable which may be used eifectively as the apex valve 18.

In the embodiment shown in FIGURE 2, the configuration or pattern 24 ofthe underflow, being indicative of the operating efilciency of thecyclone, is utilized to automatically vary the input load to the cycloneso that operation at maximum efiiciency will be assured.

In a typical ore-grinding circuit, the ore is discharged from thestorage vessel 44 through outlet 45 and onto a conveying means such asthe continuous belt conveyor 46. The variable speed control 47 operatesto vary the speed of the belt conveyor 46, and, as will be explained,such variation is accomplished automatically in response to a change inthe pattern 24 of the underflow. The ore then passes from the conveyor46 into the grinding mill hopper 43 and thence into the grinding mill49. The ground ore is discharged from the mill 49 into a hopper 5t) andconducted to a pump 51. The discharge line 51a of the pump 51 isconnected to the inlet conduit 14 and inlet nozzle 13 of the cyclone 10.The cyclone 10 then operates in the manner previously discussed, and theproper size finished material carries over through the overflowdischarge elbow 16 with the coarser materials being discharged in theunderflow. The coarse underflow discharges into a hopper 52 which, inturn, discharges into grinding mill hopper 43 to recycle the material tothe grinding mill 49.

The sensing elements or probes 29 and 30 are properly located inrelation to the underflow to be contacted by the outer surface of saidunderflow in the manner discussed previously. When the cyclone isoperated under underload conditions, the outer surface of the underflowpattern moves outwardly and, upon reaching the outer limit line 24b,comes into contact with probe 29. The contact between the underflow andthe outer probe 29 completes an electrical circuit to an electricalcontrol means 53 by means of electrical leads 54 and 55. The completingor closing of this circuit causes the control means 53 to actuate thevariable speed control 47, thereby increasing the speed of the conveyorbelt 46. The input load to the cyclone It is thus increased until theouter surface of the underflow pattern moves inwardly into the preferredrange A and out of contact with the probe 29, at which time the circuitto the control means 53 is opened. The control means 53, in response tothe opening of the aforesaid circuit, is thereby inactivated, and thepoint to which the control 47 was adjusted is maintained to therebymaintain the speed of the conveyor belt 46.

When the cyclone 10 is overloaded, the outer surface of the underflowpattern moves inwardly out of the preferred range A, and contact betweenthe inner probe 3% and the underflow is broken. This loss of contactopens the electrical circuit formed by the material, the inner probe 39,electrical lead 56, control means 53, electrical lead 55, and theunderflow tailpipe 19. The control means 53, in response to the openingof the last mentioned circuit, actuates the variable speed control 47 todecrease the speed of the conveyor belt 46, thereby decreasing the inputload to the cyclone 10. As the input load is decreased, the outersurface of the underflow pattern begins to move outwardly and willcontinue to so move until said outer surface is within the preferredrange A and contact is again made with the inner probe 30. The controlmeans 53, in response to the reclosing of the electrical circuit,maintains the variable speed control 47 at its adjusted level tomaintain the speed of the conveyor belt 46 at that point.

Thus, the outer surface of the underflow pattern, being indicative ofthe operating efilciency of the cyclone 10, is automatically maintainedwithin the preferred range A by automatically varying the input load tothe cyclone 10 in response to changes in the underflow pattern 24.

From the foregoing, it is apparent that the underflow pattern orconfiguration 24 is utilized to control the operating conditions of thecyclone 19 so that maximum efficiency and optimum separation areobtained. Although the control of the discharge orifice of the cyclonehas been described separately from control of the input load to thecyclone, it is evident that both types of control could be combined,whereby the size of the orifice as well as the volume of feed may besimultaneously adjusted. Also, the alarm or signal can be employedseparately or in conjunction with the automatic control systems.

The embodiment of the invention shown in FIGURE 1, wherein the sensingelements 29 and 30 control the pressure to the apex valve 18, lendsitself additionally to controlling the volume of cyclone underflowdischarge by regulating the feed or input load which is directed to theclassifier. For accomplishing this purpose, the pressure which is actingwithin the flexible annulus 22 of the valvih is utilized to control thespeed of the feed conveyor belt 6%, which is shown schematically inFIGURE 1 and which would feed the material to a grinding circuit andultimately to the classifier 14 in a manner similar to that shown inFIGURE 2. a

It is desirable to maintain the cyclone underflow load within a rangebetween predetermined limits; if the upper load limit is exceeded, whichwould represent too high a feed rate, the speed of the conveyor belt 60should be reduced, whereas if the cyclone underflow falls below thelower load limit, the speed of said conveyor belt should be increased.

As has been explained, the apex valve 18 controls the size of thedischarge opening 21, and the volume of the material discharging throughsaid opening is a function of the size of the opening which, in turn, isa function of the pressure within the flexible annulus 22. The pressurein said annulus is conducted through a pressure line 61 to an upper loadlimit pressure-actuated switch 62 and a lower load limitpressure-actuated switch 63. The load limit switches 62 and 63 areassociated with a variable speed control 64 which drives the conveyorbelt 60 through suitable drive means 65. So long as the pressure in theannulus is within the range defined by the adjustment of the load limitswitches 62 and 63, the conveyor belt 60 operates at a predeterminedconstant speed to maintain a constant input load.

Under overload conditions, the sensing element 30 reacts to reduce thepressure in the annulus 22 in the manner heretofore described. If thispressure reduction is within the range defined by the load limitswitches, the speed of the conveyor belt 60 is unchanged. If, however,this pressure reduction is below the predetermined limit, it actuatesthe upper load limit switch to decrease the input load to maintain thevolume of feed to the classifier and thereby maintain the underflowdischarge from said classifier within the desired range.

Similarly, under underload conditions the sensing element 29 willfunction to increase the pressure in the annulus 22, and so long as thispressure is within the predetermined limit the lower load limit switch63 remains inactive. However, if the pressure in the annulus increasesbeyond the point for which the lower load limit switch is set, saidswitch is operated to increase the speed of the conveyor belt 60 toincrease the input load to the classifier. The load limit switches,controlled by the pressure in the annulus, thereby control input load tomaintain the volume of underflow discharge from the classifier within adesired or predetermined range. It is noted that said switches are in anoverriding relationship to the sensing elements, and, while the switchescontrol the range of the underfiow discharge volume, the sensingelements control the discharge pattern within that range.

The foregoing disclosure and description of the invention areillustrative and explanatory thereof, and various changes in the size,shape and materials, as well as in the details of the illustratedconstruction, may be made within the scope of the appended claimswithout departing from the spirit of the invention.

We claim:

1. In combination, a cyclone classifier and a sensing apparatus forsensing the position of the outer surface of the substantially conicalunderllow discharge pattern of the cyclone classifier including, asensing means located in a position to define a range within which theouter surface of said pattern is to be maintained, and means formingpart of the sensing means for generating signals when said outer surfaceof the pattern is not within the defined range.

2. In combination, a cyclone classifier and a sensing apparatus forsensing the position of the outer surface of the substantially conicalunderfiow discharge pattern of the cyclone classifier, including, asensing means located in a position to define a range within which theouter surface of said pattern is to be maintained, means forming part ofthe sensing means for generating signals when said outer surface of thepattern is not within the defined range, and an indicating meansactuated by the signal generating means to indicate the position of theouter surface of the pattern relative to the defined range.

3. In combination, a cyclone classifier and a sensing and controllingapparatus for sensing and controlling the position of the outer surfaceof the substantially conical underfiow discharge pattern of the cycloneclassifier including, a sensing means located in a position to define arange within which the outer surface of said pattern is to bemaintained, and means actuated by the sensing means for varying theconfiguration of the discharge pattern to maintain the outer surface ofsaid pattern within the range defined by said sensing means.

4. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underfiowdischarge pattern of a cyclone classifier wherein said classifier isprovided with a variable underflow discharge opening, said apparatusincluding, a sensing means located in a position to define the rangewithin which the outer surface of said pattern is to be maintained, andmeans responsive to the sensing means for varying the size of thedischarge opening to thereby control the portion of said outer surfaceand maintain it within the range defined by said sensing means.

5. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern of a cyclone classifier including, a sensing meanslocated in a position to define a range within which the outer surfaceof said pattern is to be maintained, and means responsive to the sensingmeans for controlling the input load to the classifier to therebycontrol the position of said outer surface and maintain it within therange defined by said sensing means.

6. In combination, a cycline classifier and an apparatus for controllingthe configuration of the substantially conical underfiow discharge ofsaid cyclone classifier, said substantially conical underflow dischargehaving an outer surface and an axis perpendicular to the base of saidsubstantially conical underflow discharge and extending through the apexof said substantially conical underfiow discharge pattern, saidapparatus including, a first sensing means located to be contacted bysaid underfiow discharge when the outer surface of said underfiowdischarge exceeds a preselected angle relative to the axis of theunderflow, a second sensing means located to be non-contacted when theouter surface of said underflow discharge falls below a preselectedangle relative to the axis of the underfiow, and means responsive to thecontact and noncontact of said underfiow with said first and secondsensing means for varying the configuration of said underfiow dischargeto maintain the pattern within preselected limits.

7. An apparatus for controlling the configuration of the substantiallyconical underfiow discharge of a cyclone classifier wherein saidclassifier is provided with a variable underfiow discharge opening, saidsubstantially conical underfiow discharge having an outer surface and anaxis perpendicular to the base of the cone and extending through theapex of said cone, said apparatus including, a first sensing meanslocated to be contacted by said underflow discharge when the outersurface of said underfiow discharge exceeds a preselected angle relativeto the axis of the underfiow, a second sensing means located to benon-contacted when the outer surface of said underflow discharge fallsbelow a preselected angle relative to the axis of the underflow, andmeans responsive to the contact and non-contact of said underflow withsaid first and second sensing means for varying the size of thedischarge opening to thereby control the configuration of the underfiowdischarge pattern to maintain the pattern within preselected limits.

8. An apparatus for controlling the configuration of the substantiallyconical underfiow discharge of a cyclone classifier, said substantiallyconical underfiow discharge having an outer surface and an axisperpendicular to the base of said substantially conical underfiowdischarge and extending through the apex of said substantially conicalunderfiow discharge pattern, said apparatus including, a first sensingmeans located to be contacted by said underfiow discharge when the outersurface of said underfiow discharge exceeds a preselected angle relativeto the axis of the underfiow, a second sensing means located to benon-contacted when the outer surface of said underfiow discharge fallsbelow a preselected angle relative to the axis of the underfiow, andmeans responsive to the contact and non-contact of said underflow withsaid first and second sensing means for controlling the input load tothe classifier to thereby control the configuration of said underfiowdischarge to maintain the pattern within preselected limits.

9. A sensing apparatus for sensing the position of the outer surface ofthe substantially conical underflow discharge pattern of a cycloneclassifier including, a first probe located in a position to define theoutermost limit of a preselected range within which the outer surface ofsaid pattern is to be maintained, a second probe located in the path ofthe material discharging from the classifier in a position to define theinnermost limit of said preselected range within which the outer surfaceof said pattern is to be maintained, a first electrical circuit in whichthe first probe and discharging material are connected whereby saidmaterial completes said first electrical circuit when the materialcontacts said first probe, a second electrical circuit in which saidsecond probe and discharging material are connected whereby the saidmaterial completes the said second circuit when the material contactssaid second probe, means actuated by the closing of the said firstcircuit caused by said material contacting said first probe to generatea signal indicative of the outer surface of the said underflow patternbeing outwardly of the outermost limit of the preselected range, andmeans actuated by the opening of the said second circuit caused by saidunderflow discharge material moving out of contact with said secondprobe to generate a signal indicative of the outer surface of theunderflow discharge pattern being inwardly of the innermost limit ofsaid preselected range.

10. The sensing apparatus as set forth in claim 9, together with anindicating means actuated by the signal generating means to indicate theposition of the outer surface of the underflow discharge patternrelative to the preselected range.

11. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern of a cyclone classifier wherein said classifier isprovided with a variable underflow discharge opening, said apparatusincluding, a first probe located in a position to define the outermostlimit of a preselected range within which the outer surface of saidpattern is to be maintained, a second probe located in the path of thematerial discharging from the classifier in a position to define theinnermost limit of said preselected range within which the outer surfaceof said pattern is to be maintained, a first electrical circuit in whichthe first probe and discharging material are connected whereby saidmaterial completes said first electrical circuit when the materialcontacts said first probe, a second electrical circuit in which saidsecond probe and discharging material are connected whereby the materialcompletes said second circuit when the material contacts the secondprobe, means actuated by the closing of the said first circuit caused bysaid material contacting said first probe to generate a signalindicative of the outer surface of said underflow pattern beingoutwardly of said outermost limit of the preselected range, meansactuated by the opening of the said second circuit caused by saidunderflow discharge material moving out of contact with said secondprobe to generate a signal indicative of the outer surface of theunderflow discharge pattern being inwardly of said innermost limit ofsaid preselected range, and means responsive to said signal generatingmeans for varying the size of the discharge opening to thereby controlthe configuration of the pattern and maintain its outer surface withinthe said preselected range.

12. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern of a cyclone classifier including, a first probelocated in a position to define the outermost limit of a preselectedrange within which the outer surface of said pattern is to bemaintained, a second probe located in the path of the materialdischarging from the classifier in a position to define the innermostlimit of a preselected range within which the outer surface of saidpattern is to be maintained, a first electrical circuit in which thefirst probe and discharging material are connected whereby said materialcompletes said first electrical circuit when the material contacts saidfirst probe, a second electrical circuit in which said second probe anddischarging material are connected whereby the said material completessaid second circuit when the material contacts said second probe, meansactuated by the closing of the said first circuit caused by saidmaterial contacting said first probe to generate a signal indicative ofthe outer surface of said underflow pattern being outwardly of saidoutermost limit of said preselected range, means actuated by the openingof the said second circuit caused by said underflow discharge materialmoving out of contact with said second probe to generate a signalindicative of the outer surface of the underflow discharge pattern beinginwardly of said innermost limit of said preselected range, and meansresponsive to said signal generating means for controlling the 10 inputload to the classifier to thereby control the configuration of thedischarge pattern and maintain its outer surface within the saidpreselected range.

13. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern of a cyclone classifier having a discharge opening,said apparatus including, an annular flexible valve element adjacent tosaid opening and having a bore which forms a discharge orifice for saidclassifier, means for admitting and releasing pressure fluid to and fromthe interior of said valve element to change the size of its bore andthereby vary the size of the discharge orifice, a sensing means locatedin a position to define a range within which the outer surface of saidpattern is to be maintained, means forming part of the sensing means forgenerating signals when said outer surface of the pattern is not withinthe defined range, and means actuated by said signals to control theadmission and release of pressure fluid to and from said valve elementto thereby control the size of the discharge orifice to maintain theouter surface of said pattern within the defined range.

14. The sensing and control apparatus as set forth in claim 13, togetherwith a feeding means for conducting material to the classifier, avariable speed actuator for said feeding means, and means forcontrolling the said variable speed actuator by the pressure in the saidflexible valve element.

15. The sensing and control apparatus as set forth in claim 13, togetherwith a feeding means for conducting material to the classifier, avariable speed actuator for said feeding means, and upper load limitmeans actuated when the pressure in said valve element falls below apredetermined point for operating the variable speed actuator at adecreased speed, and a lower load limit means actuated when the pressurein the valve element exceeds a predetermined point for operating thevariable speed actuator at an increased speed.

16. The combination with an ore-grinding circuit having a feed inletconveyor, a grinding mill, a cyclone classifier having a substantiallyconical underflow discharge pattern, said substantially conicalunderflow dis charge pattern having an outer surface, and means forrecycling a portion of the ore through said mill, of a control apparatusincluding, a sensing means located in a position to define a rangewithin which the outer surface of said pattern is to be maintained, andmeans forming part of the sensing means for generating signals when saidouter surface of the pattern is not within the defined range, and meansactuated by said signal generating means for varying the speed of theinput conveyor to vary the input load through the grinding circuit whichvaries the load to the classifier to thereby control the configurationof the underflow discharge pattern of the classifier and maintain theouter surface of said underflow discharge within the range defined bysaid sensing means.

17. A sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern of a classifier having a discharge opening, saidapparatus including, a variable valve element adjacent to said openingand having a bore which forms a discharge orifice for said classifier,means for admitting and releasing pressure fluid to and from theinterior of said valve element to change the size of its bore andthereby vary the size of the discharge orifice, a sensing means locatedin a position to define a range Within which the outer surface of saidpattern is to be maintained, means forming part of the sensing means forgenerating signals when said outer surface of the pattern is not withinthe defined range, and means actuated by said signals to control theadmission and release of pressure fluid to and from said variable valveelement to thereby control the size of the discharge orifice to maintainthe outer surface of said pattern within the defined range, a feedingmeans for conducting material to said classifier, a variable speedactuator for said feeding means, and means for controlling said variablespeed actuator by the pressure in said valve element.

18. The combination with an ore-grinding circuit having a feed inletconveyor, a grinding mill, a cyclone classifier having a dischargeopening, and means for recycling a portion of the ore through said mill,of a sensing and control apparatus for sensing and controlling theposition of the outer surface of the substantially conical underflowdischarge pattern from said classifier, said apparatus including anannular flexible valve element adjacent to said opening and having abore which forms a discharge orifice for said classifier, means forincreasing and decreasing the fluid pressure in the interior of saidvalve element to change the size of its bore and thereby vary the sizeof the discharge orifice, a sensing means located in a position todefine a range within which the outer surface of said pattern is to bemaintained, means forming part of the sensing means for generatingsignals when said outer surface of the pattern is not within the definedrange, means actuated by said signals to increase and decrease the fluidpressure in the valve element to thereby control the volume of theunderflow discharge and to maintain the outer surface of the underfiowdis- References Cited in the file of this patent UNITED STATES PATENTS1,413,934 Ramsey Apr. 25, 1922 1,621,474 Blomfield Mar. 15, 19272,506,775 Calabrese May 9, 1950 2,648,433 Wright Aug. 11, 1953 FOREIGNPATENTS 808,914 Great Britain Feb. 11, 1959 OTHER REFERENCES ChemicalEngineering, June 1955, Volume 62, Number 25 6, pages 234-238, WetCyclones, Tangel and Brison.

1. IN COMBINATION, A CYCLONE CLASSIFIER AND A SENSING APPARATUS FORSENSING THE POSITION OF THE OUTER SURFACE OF THE SUBSTANTIALLY CONICALUNDERFLOW DISCHARGE PATTERN OF THE CYCLONE CLASSIFIER INCLUDING, ASENSING MEANS LOCATED IN A POSITION TO DEFINE A RANGE WITHIN WHICH THEOUTER SURFACE OF SAID PATTERN IS TO BE MAINTAINED, AND MEANS FORMINGPART OF THE SENSING MEANS FOR GENERATING SINGLES WHEN SAID OUTER SURFACEOF THE PATTERN IS NOT WITHIN THE DEFINED RANGE.